1. Field of the Invention
The invention relates to a method and a device for filling of an inkjet supply system in an inkjet printer, wherein the nozzle printhead is fed by an ink storage container and/ or a nozzle printhead tank connectable to the ink storage container and wherein the nozzle printhead is connected to a cleaning station with an exhaust pump for cleaning purposes.
2. Brief Description of the Background of the Invention Including Prior Art
The nozzle print head comprises essentially an arrangement of a plurality of fine nozzles (with a diameter of several micrometers), wherein likewise fine ink droplets are ejected from the fine nozzles resulting in a print picture and wherein the fine nozzles are controlled by electrical pulses. The nozzles are supplied with ink by the relatively small nozzle printhead tank disposed near the nozzle printhead. The nozzle printhead tank is connected to the ink supply system comprising the ink storage container and the ink feed lines through a connecting sleeve. A very fine meshed sieve is furnished in the nozzle printhead tank, wherein the very fine meshed sieve protects the nozzles against dirt particles and air bubbles, since these upon their penetration into the nozzles would interfere with the printing.
Upon putting the inkjet printer into service and upon change of the ink storage container, air passes into the ink supply system. Nevertheless the nozzle printhead tank has to be filled with ink.
The sieve disposed in the nozzle printhead tank prevents however that under standard conditions the air disposed at that location can escape through the nozzles. In this phase a sufficient filling of the nozzle printhead tank is not possible. However the nozzle printhead tank has to be continuously filled with a minimal amount of ink in order to be able to maintain a sufficient ink flow to the nozzles in case of intensive printing. It is necessary for this purpose that a large part of the sieve face is covered with ink. For the case that the sieve is predominantly covered by air, then the air blocks a too large part of this sieve for the ink flow and the nozzle function is interrupted. This situation is also not remedied by generating a high under pressure at the nozzles with the aid of the suction pump through the cleaning station. The suction process leads only to the situation that depending on the already present degree of filling of the nozzle printhead tank, predominantly ink is being suctioned of, which ink can press by at the sieve under the high under pressure. As soon as again a smaller under pressure prevails at the nozzles, and then air blocks again partially the ink flow and interrupts thereby again the nozzle function.
It is an object of the present invention to feed the nozzle printhead tank with an ink amount substantially corresponding to the volume of the nozzle printhead tank.
These and other objects and advantages of the present invention will become evident from the description which follows.
The present invention provides that the set object is resolved by having the ink, which ink in general is mixed with air, disposed in a two part subdivided nozzle printhead tank, wherein the part chambers of the printhead nozzle tank are separated by a fine meshed sieve, exhausted off through the nozzles in the time period until a reduced air bubble is formed in the chamber in front of the nozzle inputs. A large amount of ink is thereby stored relative to the volume, wherein a special effect is generated, which special effect was determined by experiments. It proves to be very important that at least a small air bubble is disposed in the nozzle printhead tank. High accelerations, concussions, shocks, then oscillations occur in ink jet printers with high printing speed doing printing and based on the back and forth moving of the printhead""s carriage, which high accelerations, concussions, shocks and oscillations can lead to pressure variations in the ink supply system up to the nozzle printhead. It has been shown that already a reduced air bubble in the nozzle printhead tank is sufficient to damp these pressure variations such that no interferences occur in the nozzles. Such interferences therefore are avoided by having the air bubble small relative to the overall volume of the nozzle printhead tank and the desired uniform ink flow to the nozzles occurs. Upon replacement of the ink volume in the first part chamber, the second part chamber is freed from the thereby penetrating air just to such an extent that that the ink flow to the nozzle head is not interfered with, however an air bubble remains in the second part chamber in order for the interferences, which are entered into the ink supply by moving of the nozzle head on the print carriage, to be effectively kept away from the nozzles and thereby not interfering with the nozzle function.
According to further steps it is furnished that a valve disposed in the ink supply line to the nozzle printhead is closed, that thereafter a high under pressure is generated over the exhaust pump in the cleaning station with closely placed nozzle printhead, such that upon reaching of a predetermined under pressure high level the valve is opened and thereupon the exhaust pump is turned off. During generation of the under pressure, the under pressure is not only generated in the cleaning station, but also between cleaning station and nozzle printhead in the nozzle region and in the nozzle printhead tank. The closed valve does not permit an inflow of ink from the ink supply container. The air bubble present in the nozzle printhead extends in this phase in analogy to the gas laws more and more. The expansion can however occur only through this sieve and through the nozzles in the direction toward the pump, since the rearward nozzle region is blocked by the ink and by the valve. As soon as a predetermined under pressure (depending on the exhaust time, the sealing of the connection between the cleaning station and the nozzle region, the power of the pump) prevails, then the valve is opened. Upon opening suddenly ink can continually flow from the supply region. The under pressure in the ink supply system collapses and the air bubble shrinks again corresponding to the standard pressure. The volume released in the printhead tank is filled by the continually flowing ink and the ink level in the printhead tank rises to a higher level. The air already passed through the sieve and the nozzles does not again return into the printhead tank. This process effects that the printhead tank is filled to a large extent with ink, however the residual air bubble remains corresponding to the pressure situations. Therewith the recited requirements for a substantial filling of the printhead tank and the generation of a residual air bubble are fulfilled.
Alternatively one can now proceed after further steps in such a way that a valve, which is connected to the storage container generates a high under pressure in an exhaust line from the suction region or from the cleaning station such that after a predetermined under pressure height level, the valve is opened and thereafter the exhaust pump is turned off. Several advantages are thereby achieved, which in part are also advantageous relative to the device technology. A reduction of the mass to be carried along on the printhead""s carriage is achieved in addition to the substantial filling of the printhead tank and the formation of the air bubble.
The device for the filling of the ink supply system in an inkjet printer with a nozzle printhead, and ink storage container, and a printhead tank connected to the ink storage container or connectable to the ink storage container disposed on the printhead carriage, furthermore with a cleaning station, wherein the nozzle printhead is sealingly movable to the cleaning station and an exhaust pump connected to the cleaning station, resolves the object of the present invention by having the nozzle printhead with the nozzle inputs placeable at the cleaning station and the nozzle inputs connected to a first nozzle printhead tank part chamber, wherein the first nozzle printhead tank part chamber is separated from a second printhead tank part chamber adjoining to the first printhead tank part chamber. The advantage is the substantial filling of the nozzle printhead tank part chambers while simultaneously forming an air bubble of a predetermined size, which air bubble serves for damping the printhead""s carriage motions, that is of the accelerating and delaying forces.
Further features to serve for the arrangement of device components advantageous for the performance of the method. An electrical, pneumatic, or mechanical controllable valve is disposed in the ink supply line between the first printhead tank part chamber or the second printhead tank part chamber and the ink storage container.
The valve can also be disposed close to the cleaning station.
Another variation results from having a storage container as a buffer volume disposed between the valve and the suction pump. The valve is closed after sealingly placing the nozzle printhead at the cleaning station and a high under pressure is generated in the buffer volume with the exhaust pump. Upon opening of the valve after reaching of the high under pressure and after switching off of the exhaust pump, the generated air bubble expands quickly, which however can occur only through the sieve and through the nozzles in the direction of the exhaust pump. The rearward path is blocked by continual flowing ink. The under pressure collapses and the air bubble shrinks to a measure corresponding to standard pressure. The volume in the print head tank part chambers is filled by continual flowing ink. The buffer volume is associated with the advantage that the generated under pressure does not collapse too quickly after opening of the valve.
It is proposed according to further features to furnish a branching in the ink supply line between the valve and the exhaust pump, wherein the storage container for the buffer volume is connected to the branching. The valve does not have to be disposed here on the printhead carriage. The mass disposed on the printhead carriage is thereby reduced and the acceleration and delaying forces are smaller.
An improvement further comprises that the exhaust line itself forms the buffer volume by the longitudinal section increased in its diameter and or its length.
Embodiments of the invention are illustrated in the wall in which are explained in more detail in the following and by way of which also the method is illustrated.
The novel features which are considered as characteristic for the invention are set forth in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.